[Amps] MOSFET amp filtering - was: auto-tune

[Jim Brown]

On Fri,12/16/2016 6:37 AM, Jim Thomson wrote:
> ##    Excellent presentation.

Thanks, but although I used Power Point to show the data, it's really 
just an engineering report on lab work that I have done. And the only 
place it's been presented is as this file on the internet.

> ##  The k3 is a superb radio for cw.   But its  -29 db pep  IMD3 on tx,  is nothing to brag about.   The dishtronix at
> -30 db pep IMD3 is no better.

2-tone IMD measurements are NOT the be-all and end-all of describing a 
radio's performance. In ARRL Lab tests, the K3 showed the same superior 
CW keying bandwidth that I measured, and when it was introduced in 2008, 
was by far the best in that regard that ARRL had ever tested. The 
current version, the K3S, introduced in 2014, is roughly 8-10 dB better! 
And all it takes to make that improvement to a 2008 K3 is to replace the 
synthesizer board, at a cost of about $250, and it's an easy field 
replacement.

But back to IMD -- it is well known, and Elecraft says so, that IMD 
performance improves a lot when the output power is reduced to the 50W 
range, which is what it takes to drive most commercial power amps. K6XX, 
who works for Elecraft, showed that in a talk he gave to the Northern 
California Contest Club in 2013. It's on my website. Note that he was 
NOT praising the radio -- the talk was about how to transmit the 
cleanest possible signal. I contributed to the talk with on-air 
measurements of some local signals that were driving both of us nuts, 
and with a disciplined series of a neighbor's IC7600 (with his 
cooperation).

http://k9yc.com/K6XXAmpTalk.pdf

73, Jim K9YC